1. Field of the Invention
The present invention relates to a measurement method and apparatus which are, for example, used in an ion implantation apparatus, for receiving ion beam scanned in an X direction and measuring the waveforms of beam currents flowing into a plurality of beam detectors in a beam monitor in which the plurality of beam detectors are arranged at the same interval in the X direction (for example, a horizontal direction, the same applies to the following).
2. Description of the Related Art
FIG. 1 is a schematic plan view showing an example of an ion implantation apparatus. This ion implantation apparatus includes an ion source 2 for emitting ion beam 4, a mass separator 6 for receiving the ion beam from the ion source 2 and separating and taking out the ion beam 4 with an intended mass from the ion beam 4, an accelerator/decelerator 8 for receiving the ion beam 4 from the mass separator 6 and accelerating or decelerating the ion beam 4, an energy separator 10 for receiving the ion beam 4 from the accelerator/decelerator 8 and separating and taking out the ion beam 4 having intended energy from the ion beam 4, a scanner 12 for receiving the ion beam 4 from the energy separator 10 and scanning the ion beam 4 in the X direction, a beam parallelizer 14 for receiving the ion beam 4 from the scanner 12, bending the ion beam 4, and scanning the ion beam 4 in parallel in the X direction in cooperation with the scanner 12, and a wafer moving apparatus 20 for mechanically reciprocally scanning (reciprocation) a wafer 16 in a Y direction (for example, a vertical direction, the same applies to the following) substantially perpendicular to the X direction in an irradiation region of the ion beam 4 from the beam parallelizer 14.
When the design traveling direction of the ion beam 4 emitted from the beam parallelizer 14 is set to a Z direction, two directions which are substantially perpendicular to each other in a plane substantially perpendicular to the Z direction are the X direction and the Y direction. The ion beam 4 emitted from the beam parallelizer 14 is substantially scanned in parallel with the design traveling direction Z. This is called parallel scanning. The “design traveling direction” is a predetermined traveling direction, that is, an originally traveling direction.
The mass separator 6 is, for example, an electric magnet for mass separation, which separates the mass of the ion beam 4 by a magnetic field. The accelerator/decelerator 8 is, for example, an accelerating/decelerating tube which has a plurality of electrodes and accelerates/decelerates the ion beam 4 by an electrostatic field. The energy separator 10 is, for example, an electric magnet for energy separation, which separates the energy of the ion beam 4 by a magnetic field. The scanner 12 is, for example, a scanning electric magnet for scanning the ion beam 4 by a magnetic field. The beam parallelizer 14 is, for example, an electric magnet for beam parallelization, which parallelizes the ion beam 4 by a magnetic field. The wafer moving apparatus 20 has a holder 18 for holding a wafer 16.
By the above-described configuration, the ion beam 4 with the desired mass and the intended energy is scanned in parallel in the X direction and is irradiated on the wafer 16. The wafer 16 is mechanically reciprocally scanned in the Y direction relative to the ion beam 4 and the ion beam 4 is irradiated onto the entire surface of the wafer 16 so as to implant ions. A method of performing both the electromagnetic scanning of the ion beam 4 and the mechanical scanning of the wafer 16 is called a hybrid scanning method.
In the above-described ion implantation apparatus, for example, for parallelism measurement of the ion beam 4 or shaping of the scanning waveforms of the ion beam 4, it is important to measure the waveforms (that is, a temporal variation) of the ion beam scanned in the X direction at a plurality of positions in the X direction in vicinity of the wafer 16 because of increasing size of the wafer 16 and miniaturization of a semiconductor apparatus formed on a surface of the wafer 16.
Conventionally, the measurement of the waveforms of the beam currents of the ion beam 4 was performed by a measurement method shown in FIG. 2 or 3. In either method, a beam monitor 30 which a plurality (for example, ten to several tens) of beam detectors 32 for receiving the ion beam 4 and detecting the beam currents Ib are arranged at the same interval in the X direction is provided in the vicinity of an upstream or a downstream side of the wafer 16, and the beam monitor 30 receives the ion beam 4 scanned in the X direction as denoted by an arrow B and measures the waveforms of the beam currents flowing into the beam detectors 32. Each of the beam detectors 32 is, for example, a Faraday cup.
In the measurement method shown in FIG. 2, the beam detectors 32 configuring the beam monitor 30 are connected to one currents measurement apparatus 40 through switches S, the switches S are sequentially switched on one by one (that is, selectively). The waveforms of the beam currents Ib flowing into the beam detectors 32 are sequentially measured using the currents measurement apparatus 40. The switching of the switch S is performed between measurement processes. That is, a process is repeated by scanning the ion beam 4 to perform the measurement, switching a switch S and scanning the ion beam 4 to perform the measurement.
An example of the beam currents waveforms measured using the currents measurement apparatus 40 is shown in FIG. 4. The beam currents waveforms similar to (is not necessarily equal to) that shown in FIG. 4 is obtained by each of the beam detectors 32. Since the scan speed of the ion beam 4 is substantially constant, the horizontal width of the beam currents waveforms varies according to a beam width (see a beam width Wb shown in FIG. 6) of the ion beam 4 in the X direction and the height thereof varies according to the beam currents density of the ion beam 4.
In Japanese Patent No. 3456318 (paragraph [0009], FIG. 6), a measurement method using one currents measurement apparatus (beam currents converter) in a beam monitor (multi-point beam monitor) in which n conductors are led out is disclosed and corresponds to the measurement method shown in FIG. 2.
In the measurement method shown in FIG. 3, currents measurement apparatus 40 is respectively connected to the beam detectors 32 configuring the beam monitor 30 and the waveforms of the beam currents Ib flowing into the currents measurement apparatus 40 are simultaneously measured. The beam current waveforms measured using the current measurement apparatus 40 are, for example, equal to that shown in FIG. 4.
In the measurement method shown in FIG. 2, since the number of current measurement apparatus 40 is one, all the beam detectors 32 become equal in measurement precision. However, since the switches S of the beam detectors 32 are sequentially switched on one by one so as to measure the beam current waveforms, the measurement is time-consuming.
Although the switches S are switched at a high speed, since a standby time due to switching delay times of the switches S or a response delay time of the current measurement apparatus 40 is required, there is a speed-up limitation. In addition, the life spans of the switches S may be reduced or reliability of connection may deteriorate.
In the measurement method shown in FIG. 3, the waveforms of the beam current flowing into all the beam detectors 32 can be measured for a short period of time. However, since the current measurement apparatus 40 is respectively provided in the beam detectors 32, it is difficult to equalize the measurement precision of the current measurement apparatus 40. Accordingly, the measurement precision deteriorates. In addition, the number of current measurement apparatus 40 is large.